James b



w is? 1!] i vblliifi ATTORNEYS.

{No Model.)

, J. B. ALLPREE.

BALANUED SLIDE VALVE.

V Patented July 10, 1883 UNITED STATES PATENT @FFICE JAMES B. ALLFREE,or CUMBERLAND, MARYLAND.

Y BALANCED LlDE-VALVE.

SPECIFICATION forming part of Letters Patent No. 280,993, dated July 10,1883.

Application filed April 27, 1883. (N model.)

To all whom it may concern:

.Be it known that 1, JAMES B. ALLFREE, a citizen of the United States,residing at Cumberland, in the county of Allegheny and State ofMaryland, have invented a new and useful Improvement in BalancedSlide-Valves, of which the following is a specification.

My invention relates to that class of slide valves which operate in thechests of engines to admit and emit steam to and from the cylinders, andare called balanced valves. It is a well-kn own fact in en gine-runningthat when the steam is suddenly shut off the reaction on the valves issevere, causing them to thump. The same result is also sometimesproduced when the steam condenses into water by being let into a coldengine. To guard against injury to the valves and steam-chests from suchshocks, it is common'to provide balanced valves with springs, whichallow the valves to yield.

The object of my invention is to provide means whereby valves havingsuch springs may yet be restrained from pressing unduly against thevalve-seats or the walls of the steam-chest. To this end my inventionconsists in the construction and combination of 3. "Fig. 2 isalongitudinal vertical section of the parts forming a double slide-valve,hereinafter described and claimed, reference being had to theaccompanying drawings, in which- Figure 1 is a side elevation of myvalve.

same; and Fig. 3 is an end view of the valve on a reduced scale, showingalso a portion of a cylinder.

A represents the valve, which consists of two parts, a a, which areduplicates of each other, and are, in fact, two valves turnedback toback, each one seated, as usual, over the parts of the steam-chest. Thetwo faces ff of said chest forming said seats are perfectly parallelwith each other. The two parts a a of the valve are pressed upon theirseats by springs 12, which act between said parts to separate them.

0 represents one or more openings through both parts a a, from face toback, to allow steam to circulate behind the valves. This wouldnaturally press each valve upon its seat with the'whole force of steamon every inch of the valve-back, and cause great friction and wear;

parts are nicely adjusted when the engine is being finished, and therelative proportion of the ledges to the faces of the valves is intendedto be such that the slight reciprocating motion of said ledges on eachother will wear them away at the same rate that the valve-faces will beworn in the same time, thus keeping the valves well seated, an d all thetime preventing their bearing unduly on their seats. Whenever the facesof the valves become enough worn to require facing off, the said ledgeson the valves and on the clamps will also be readjusted, so that theyrequire no attention on the part of the engineer.

h is the valve-stem, serving also as a screwbolt byhaving a right-handthread at one end, engaging a similar internal thread or nut in one ofthe clamps, d, and a left-hand thread at or near the other end of thevalve, similarly engaging the other clamp, 12. By rotating thisvalve-stem the clamps may be drawn with any desired degree of tightnesson the ends of the valve. This may be done by applying a wrench to asquared portion of the valve-stem outside of the chest without openingthe chest for such adjustment, and the rod may be fixed, as usual, toscrew-bolts by means of check-nuts. By any extreme shock upon theirfaces, these valves will be pressed upon their springs, and they will berestored to place by the normal action of the steam.

\Vhat I claim as my invention is 1. The combination, with twovalve-seats placed face to face parallel with each other, and two valvesadapted to reciprocate thereon, and having ledges upontheir ends, of twoclamps having corresponding ledges adapted to hold said valves to afixed limit of separation, and springs adapted to separate them,

as specified, whereby said valves are allowed.

to approach each other when undifly pressed,

and are rigidly restrained from pressing upon their seats, as described.

2. The combination, with two parallel valve- 5 seats, f and f, and twovalves, a and a,

adapted to slide thereon, and provided with ledges e and e, of twoclamps, (Z and d, adapted to engage said ledges, and having,respectively,

right and left screw-threads or nuts in them, and the valve-stem h,provided with right and 10 left screw-threads, and the springs 7),between the valves, as and for the purpose specified.

JAMES B. ALLFREE. Witnesses:

'SOLON O. KEMON, CHAS. A. PETTIT.

